1. Field of the Invention
The present invention relates to a method for delivering data to devices connected via a communications network.
2. Description of the Related Art
Generally, when data is delivered, a device at a delivery source must prepare the information identifying a delivery destination (hereinafter referred to as “destination information” or “delivery destination information”), and data to be delivered for each delivery destination.
FIG. 1 explains an existing general data delivering system. This figure depicts the device at a data delivery source and an external storage medium accessed by this device. Note that this system is assumed to deliver data based on a user instruction (delivery request).
A data managing unit 501 makes a data storing unit 502 collect the data corresponding to a user instruction. The data storing unit 502 obtains the data to be delivered to a user from an external storage medium 511 according to an instruction from the data managing unit 501. Then, the data managing unit 501 provides a data transferring unit 503 with the data collected by the data storing unit 502 and the destination information of that data. The data transferring unit 503 issues a data transfer instruction to a communication controlling unit 504. The communication controlling unit 504 then delivers the requested data to the user according to the data transfer instruction.
When data is delivered to a plurality of destinations with the above described system, the above stated process is repeatedly executed or a multi-cast transmission is performed if it is possible. The method repeating the above described process, however, imposes a heavy load on a device at a delivery source. On the other hand, the multi-cast transmission can only transmit the same data to all of destinations.
As a known method delivering data that differs depending on each destination, for example, Japanese Laid-open Patent Publication No. 6-152917 is known. This publication recites the technique with an improved merging capability. Hereinafter, the technique relating to Japanese Laid-open Patent Publication No. 6-152917 is explained by referring to FIGS. 2, 3A, and 3B.
FIG. 2 explains an existing data delivering system with a merging capability. This figure depicts a device at a data delivery source and an external storage media accessed by that device. Here, it is assumed that data in a common format (hereinafter referred to as “combined data”) shown in FIG. 3A is generated and delivered to each destination. The combined data is composed of a variable portion which differs depending on each destination, and a common portion which is common to all of destinations.
A data managing unit 521 makes a common data storing unit 522 collect common data which is common element data to be delivered to a destination, for example, according to a user instruction. The common data storing unit 522 then collects the common data from an external storage medium 531, and passes the collected data to the data managing unit 521. This collected data is stored in the common portion of the combined data, but its variable portion is empty at this stage.
Next, the data managing unit 521 makes a variable data storing unit 523 collect variable data. The variable data storing unit 523 therefore collects variable data from an external storage medium 532, and passes the collected data to the data managing unit 521. It should be noted that variable data includes destination information for identifying corresponding destination, and element data to be delivered to corresponding destination, for example, as shown in FIG. 3B.
The data managing unit 521 separates the variable data into the destination information and the element data. Then, the data managing unit 521 inserts (merges) element data-1 into the variable portion of the combined data, attaches destination information-1 to the combined data, and passes the combined data to a data transferring unit 524. The data transferring unit 524 issues a data transfer instruction to a communication controlling unit 525. The communication controlling unit 525 delivers the common data into which the element data-1 is inserted to the user identified by the destination information-1 according to the data transfer instruction. Thereafter, combined data into which element data-2 through element data-n are respectively inserted are delivered to respective users identified by destination information-2 through destination information-n.
In addition to the above described method, methods for delivering data that differs depending on each destination have been proposed. For example, the technique recited in Japanese Laid-open Patent Publication No. 63-16749, the technique recited in Japanese Laid-open Patent Publication No. 9-311831, etc. are proposed. With the former method, all candidate data to be inserted into a variable portion are delivered from a delivery source to destinations along with common data, and the users at the destinations respectively select necessary information. With the latter method, data is delivered in a form (image, audio, text, etc.) requested by each destination.
However, conventional data delivering methods have the following problems.
(1) A delivery source system must store all data to be delivered to corresponding destinations, or at least prepare all data to be delivered to corresponding destinations. Accordingly, the load on the delivery source system becomes heavy. Additionally, most of the known methods cannot start a data delivery until all data (to be delivered to all of destinations) are collected, when data that differs depending on each destination is delivered. Therefore a data delivery delay becomes problematic in this case.(2) A delivery source system must store the information about all of destinations (such as IP or mail addresses, system names, or the like). Therefore, the operations for managing destinations become complicated in the delivery source system.(3) A delivery source system must generate (or assemble) all of delivery data, when data that differs depending on each destination is delivered. Therefore, the load on the delivery source system becomes heavy.(4) All of delivery data are output from a delivery source system, when data that differs depending on each destination is delivered. Therefore, lines or paths adjacent to the delivery source system are occupied by that data delivery.